(i) Technical Field
The present invention relates to a fixing device, an image forming apparatus, and a fixing method.
(ii) Related Art
In an image forming apparatus, such as a copier and a printer, a roller pair system or a belt system is known as a fixing device which fixes a toner image (developer image) on, for example, a sheet (recording medium). The roller pair system is configured by a heating roller (heating rotary member) and a pressure roller (pressure rotary member). The belt system is configured by a heating unit (heating rotary member), which is formed by a heating roller and an endless heating belt driven to rotate by the heating roller, and a pressure roller (pressure rotary member).
Further, the heating rotary member, such as the heating roller and the heating unit, is provided with a heater serving as a heating source.
In such a fixing device, a sheet having an unfixed toner image transferred thereto is sent to a fixing nip part formed between mutually facing portions of a roller pair or the like, and is applied with heat and pressure. Thereby, the toner image is fixed on the sheet.
In this process, the heat of the heating rotary member is also transmitted to the pressure roller. Thus, the pressure roller is thermally deformed.